MAGNETIC-RESONANCE KNEE ARTHROGRAPHY - ENHANCED CONTRAST BY GADOLINIUM COMPLEX IN THE RABBIT AND IN HUMANS

This study contains the fundamentals and the technique of the intraarticular application of an MRI contrast agent in connection with magnetic resonance imaging (MRI arthrography). It also presents the resulting clinical relevance for knee joint diagnostics. The significance of MRI arthrography is linked above all to the central question of whether or not it is possible to depict the hyaline cartilage, its surface and its thickness with the help of MRI arthrography. MRI arthrography was used for in vitro examinations of rabbit knee joint cartilage and human joint cartilage. The in vivo application was carried out in 73 patients. Apart from the metric evaluation and the assessment of the information content of the MRI image, the corresponding histologic sections were made in 20 knee joints in order to compare the cartilage surface and the thickness of the cartilage with the results in the MRI image. The optimum amount of contrast agent for visualization was determined, the uptake and clearance of the contrast agent from the cartilage were assessed, and trace elements from the cartilage were also analyzed. The examination showed that the molecular structure of the contrast agent (gadolinium-DTPA) does not prevent the uptake of the contrast agent into the matrix of the hyaline cartilage. But this process is reversible. Thus, 14 hours after the intraarticular application of the contrast agent no measurable traces of gadolinium-DTPA could be established. The intraarticular application of the contrast agent also made it possible to achieve a constant and reproducible visualization of all joint structures. This affected mainly the surface of the hyaline cartilage. The best imaging quality was achieved with intraarticlular application of 30 to 40 mL of a 2 mmolar solution of gadolinium-DTPA. The technique used for the intraarticular application is the same as for the common procedures of knee joint aspiration. The clinical importance of MRI arthrography lies in the fact that a very detailed assessment can be made for therapy planning and furthermore in the possibility to provide the surgeon with answers to specific questions concerning the therapy. Examples are the extent and location of chondromalacia in a patient and the question whether a cartilage fracture has already occurred in osteochondrosis dissecans or not. The evaluation of cartilage together with the possibility to assess all other structures in the knee joint is a special feature of MRI arthrography. The high sensitivity and specificity of this method makes it superior to the examination without contrast agent and comparable to diagnostic arthroscopy. The main emphasis of MRI arthrography in the clinical application is in the evaluation of knee pain with an uncharacteristic clinical appearance. Other possible uses are the follow-up after surgical interventions, for example after cartilage-bone grafts. In summary, it can be said that the contrast agent gadolinium-DTPA for the intraarticular application in MRI arthrography can achieve an optimum visualization of the hyaline joint cartilage. This method is therefore an important addition to the range of diagnostic measures for the knee joint.